Publications

@article{Shen2025b,

title = {Investigation into the coupling mechanism of tailwater vortex dynamics and cavitation during pump-as-turbine operations},

author = {Jiantao Shen and Xuanwen Jia and Li Cheng and Weixuan Jiao and Bowen Zhang and Giorgio Pavesi},

doi = {10.1063/5.0287323},

issn = {10897666},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Physics of Fluids},

volume = {37},

issue = {10},

publisher = {American Institute of Physics},

abstract = {In order to investigate the coupling mechanism between tailwater vortex and cavitation bubbles (CB) during the operation of a low-head pump-as-turbine (PAT), the method of combining experiment and numerical simulation is used to quantify the vortex dynamics characteristics in combination with the vorticity transport equation under high flow conditions for PAT mode. The results show that the decrease in Thoma number significantly regulates the symbiotic evolution of tailwater vortex and CB: prolonging the residence time of CB in the draft tube (DT) and changing its evolution mode, resulting in the extension of vortex rope (VR) generation period, length contraction, and the increase in breaking vortex in DT. The peak volume of CB is 7 times that in the rotor region, squeezing the channel vortex and the wake vortex, weakening its contribution to VR. Vortex dynamics shows that the relative vortex stretching term is the core driving force of vorticity, which causes velocity gradient distortion and VR high-frequency oscillation synchronously with vertical vorticity. The baroclinic torque term (BT) only generates pulse contribution in the early stage of CB collapse. Under critical cavitation, BT converts the cavity collapse energy into vortex energy through density-pressure gradient coupling, which expands the vortex core radius to 0.03 m, increases the circulation peak to 2.3 m2/s, and shifts outward by 27.3%, resulting in vortex energy diffusion and high-frequency oscillation of the flow field. This study provides a theoretical basis for cavitation suppression and operational optimization of low-head PAT.},

key = {Cavitation, PAT, Pump as Turbine, tailwater vortex},

keywords = {Cavitation, PAT, Pump as Turbine},

pubstate = {published},

tppubtype = {article}

}

@article{Yin2025d,

title = {Compressibility characteristics of transient sheet/cloud cavitation – a numerical survey},

author = {Tingyun Yin and Giorgio Pavesi},

doi = {10.1016/j.icheatmasstransfer.2024.108560},

issn = {07351933},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {International Communications in Heat and Mass Transfer},

volume = {162},

publisher = {Elsevier Ltd},

abstract = {In this study, the transient compressible sheet/cloud cavitation around the stationary blade is investigated using a Computational Fluid Dynamics (CFD) method. The instantaneous characteristics of the cavity, such as the destabilization of the sheet cavity, the transformation of the sheet topology into the cloud topology, and the process of shrinking and collapsing of the cloud cavity, are reasonably replicated. The examination of the sheet cavity reveals that the disturbance moving upwards within the cavity is a condensation shock. This shock adheres to the classical Rankine–Hugoniot jump conditions and travels at a hypersonic speed. Once the condensation shock reaches the point where the cavity separates, the sheet cavity unlocks from the surface and transitions into a cloud cavity. The cloud cavity undergoes a reduction in size as it is carried downstream and collapses in the zone of high pressure. Investigations of a small cloud cavity reveal that its collapse results in the release of immense pressure, reaching several million Pascals. Furthermore, the relationship among potential energy, kinetic energy, and pressure wave energy during the collapse of the cavity is exposed, contributing to a more comprehensive comprehension of this intricate phenomenon.},

keywords = {Cavitation, Condensation Shock, Energy conversion, Shock Wave},

pubstate = {published},

tppubtype = {article}

}

@article{Zhao2025,

title = {Energy efficiency optimization of multistage centrifugal pumps based on blade loading control: Insights into flow instability suppression mechanism},

author = {Jiantao Zhao and Ji Pei and Zhongsheng Wang and Benying Zhang and Wenjie Wang and Xingcheng Gan and Giorgio Pavesi},

doi = {10.1016/j.energy.2025.136586},

issn = {18736785},

year  = {2025},

date = {2025-01-01},

journal = {Energy},

volume = {328},

publisher = {Elsevier Ltd},

abstract = {Multistage centrifugal pumps (MSCPs) are critical for high-pressure fluid transport, and their hydraulic efficiency directly affects the energy consumption of energy systems. However, flow instabilities result in substantial energy loss. This study employed blade loading theory, which is closely related to the flow field state, to achieve a parametric blade design. A non-expert-driven optimization framework was constructed by integrating the Metamodel of Optimal Prognosis (MoP) with the technique for order of preference by similarity to the ideal solution based on the entropy weight method (EW-TOPSIS). The optimization objective was to improve the hydraulic efficiency of the pump in the preferred operating range, with a constant pressure-boosting performance as a constraint. The results demonstrated that the efficiency improvement exceeded 2 % across the targeted operating range. Moreover, the MoP exhibited a strong predictive capability, even in multi-parameter scenarios with limited sample data. Further vortex dynamics analysis revealed that loading redistribution reduced the incidence angle, suppressed flow separation on the blade suction surface, and, under high-flow conditions, regulated the dominant vortex transport mechanisms governed by vortex diffusion and dissipation. This research demonstrated that optimizing blade loading serves as an effective passive flow control strategy for MSCPs, enabling significant improvements in energy conservation.},

keywords = {Approximate model, CFD simulation, Energy efficiency enhancement, Flow diagnosis, Inverse Design, Multistage Centrifugal Pump},

pubstate = {published},

tppubtype = {article}

}

@article{Yin2025c,

title = {Interpreting proper orthogonal decomposition modes extracted from partial cavity oscillation},

author = {Tingyun Yin and Giorgio Pavesi},

doi = {10.1063/5.0244165},

issn = {10897666},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Physics of Fluids},

volume = {37},

issue = {1},

publisher = {American Institute of Physics},

abstract = {This study employs the two-dimensional proper orthogonal decomposition approach to analyze the pressure, vapor fraction, and streamwise velocity flowfields of partial cavity oscillation. The interrelations among mode, energy ratio, temporal coefficient, and flowfield reconstruction are thoroughly examined, thereby augmenting comprehension of the cavitating flow mechanism and bubble dynamics. It is found that the first modes of the pressure, vapor fraction, and streamwise velocity flowfields contain 56.31%, 36.37%, and 31.81% energy, respectively; the decrease in energy ratio results in the variation of its temporal coefficient close to sinusoidal configurations. Moreover, the temporal coefficient of the first mode varies closely related to the flowfield-relevant variable. The first modes of the pressure, vapor fraction, and streamwise velocity flowfields are significantly different, but all have two highlighted structures closely related to the self-variable system. The strong nonlinearity and high dimensionality of the cavitation flowfield render precise reconstruction using a limited number of modes exceedingly challenging. The data approximate the original snapshot more closely when the flow field is reconstructed with a greater number of modes. Although the location with a relatively high root mean square reconstruction error is significantly different when the first nine modes are used for flowfield reconstruction, its order of magnitude is less than the self-variable system, and the order discrepancy is fixed, equal to 1.},

key = {Cavitation, Orthogonal decomposition, Cavity},

keywords = {Cavitation, Cavity, Orthogonal Decomposition},

pubstate = {published},

tppubtype = {article}

}

@article{Shen2025,

title = {Broader high-efficiency zone of micro-pumped hydro storage enabled by a variable-speed reversible mixed-flow pump: Taking acceleration as an example},

author = {Jiawei Shen and Ji Pei and Wenjie Wang and Shouqi Yuan and Giorgio Pavesi},

doi = {10.1016/j.renene.2025.123642},

issn = {18790682},

year  = {2025},

date = {2025-01-01},

journal = {Renewable Energy},

volume = {253},

publisher = {Elsevier Ltd},

abstract = {Given the burgeoning renewables-based microgrids, it is crucial for a stable power supply to enable more flexible micro-pumped hydro storage by the reversible mixed-flow pump (RMFP) with a broad high-efficiency zone (HEZ). Variable-speed operation is the most effective method to regulate operating conditions for scenarios of the RMFP without the guide vane. To reveal the effect of variable-speed regulation on the HEZ, we test the energy characteristics of RMFP at four speeds based on a bidirectional hydraulic test bench. The experiment shows that the RMFP receives an HEZ that is expanded by 53.4 % in pump mode and 60.3 % in turbine mode by accelerating from 830 r/min to 980 r/min. Moreover, the transition process of the acceleration regulation under full load is simulated based on a validated CFD numerical scheme. It is indicated that the acceleration regulation not only improves the efficiency and hydraulic dissipation but also alleviates the flow instabilities. The peak-to-peak value and the amplitude of the dominant frequency of the pressure fluctuation in the runner can be reduced by up to 49.4 % and 46.2 %, respectively. This study highlights the broad high-efficiency zone and stable internal flow that variable-speed regulation contributes to the RMFP, aiming at enhancing the flexibility of micro-pumped hydro storage.},

keywords = {Acceleration transition process, Flow instability, High-efficiency operation, Micro-pumped hydro storage, Reversible mixed-flow pump, Variable-speed regulation},

pubstate = {published},

tppubtype = {article}

}

@article{Zhang2025,

title = {Impact of the motion effect of the cutoff facility on the dynamic energy loss of the prototype axial flow pump system during the startup process},

author = {Xiaowen Zhang and Giorgio Pavesi and Chongyang Hu and Xijie Song and Fangping Tang},

doi = {10.1063/5.0250407},

issn = {10897666},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Physics of Fluids},

volume = {37},

issue = {1},

publisher = {American Institute of Physics},

abstract = {Large pumping systems have emerged as one of the primary areas of energy consumption. During the startup process (SUP) of the axial flow pump system (AFPS), a complex interaction unfolds involving the motion of the cutoff facilities (COF), the acceleration of the pump, and the phenomenon of energy dissipation. The kinematic characteristics of the COF significantly influence the flow patterns, dynamic loads, and energy transfer experienced by the system. This study investigates the energy dissipation mechanism of a prototype AFPS (PAFPS) during SUP, utilizing a combination of experiments on engine starting characteristics, computational fluid dynamics, and in-field measurements of the PAFPS. Two COF motion modes are compared, revealing that accelerated gate opening improves transition efficiency and reduces energy consumption. Key findings highlight that accelerated gate motion minimizes turbulence-induced losses near the COF exit and suppresses high entropy production regions in the impeller domain, leading to smoother and more energy-efficient operations. These insights offer actionable strategies to enhance pump system performance during SUP.},

keywords = {Axial Pump, Energy loss, Pump, startup},

pubstate = {published},

tppubtype = {article}

}

@article{Zhou2025,

title = {Analysis of hydraulic loss of the pump-jet with accelerating and decelerating ducts via entropy generation theory},

author = {Yunkai Zhou and Jianping Yuan and Yanxia Fu and Shirong Ye and Giorgio Pavesi and Giovanna Cavazzini},

doi = {10.1063/5.0273790},

issn = {10897666},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Physics of Fluids},

volume = {37},

issue = {7},

publisher = {American Institute of Physics},

abstract = {Pump-jets serve as critical propulsion systems for underwater vehicles, directly impacting navigation safety and energy efficiency. Traditional pressure-drop analysis methods, while widely adopted, exhibit limitations in spatially resolving localized energy dissipation mechanisms. This study implements entropy generation theory to systematically evaluate irreversible energy losses in pump-jet, with particular emphasis on quantifying the spatial distribution and magnitude of hydraulic losses. Through rigorous numerical investigations of accelerating and decelerating duct configurations with varying camber and attack angles, comparative analyses of energy characteristics are conducted across distinct pump-jet components. The results demonstrate that entropy generation theory proves advantageous when assessing the energy characteristics of pump-jet. Compared to accelerating duct pump-jet, the stator and pre-stator of decelerating duct pump-jet absorb a larger share of hydraulic losses, demonstrating superior hydrodynamic performance. Flow characteristics reveal that the variation of f and α leads to the significant influence on the entropy production in the flow field, while the instability mechanism of impeller and stator trailing vortices also share prominent diversity. Thus, f and α can serve as core parameters to distinguish between accelerating and decelerating ducts. Selecting appropriate parameters based on different operating conditions can significantly enhance performance and safety. Overall, this study provides thermomechanical guidelines for performance optimization through strategic geometric parameter selection under diverse operational conditions.},

keywords = {Accelerating Decelerating Ducts, Duct, Entropy, Pump Jet},

pubstate = {published},

tppubtype = {article}

}

@article{Yin2025b,

title = {Several compressible computational fluid dynamics methods applied to transient sheet/cloud cavitation},

author = {Tingyun Yin and Giorgio Pavesi},

doi = {10.1063/5.0252333},

issn = {10897666},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Physics of Fluids},

volume = {37},

issue = {2},

publisher = {American Institute of Physics},

abstract = {This paper introduces several compressible computational fluid dynamics (CFD) methods and assesses their ability to simulate typical sheet-to-cloud cavitating flow around a hydrofoil. More precisely, the Tait equation of state is used to describe the density of water, while the ideal gas equation of state is used to model the density of vapor. The first method assumes that the cavitation is a multiphase flow with isothermal conditions, meaning that it exhibits isothermal compressibility. Based on the first method, the second and third methods take into account the thermal energy and total energy equations, respectively, i.e., the thermal energy compressibility and the total energy compressibility. An incompressible simulation is also performed for the comparison. The results show that all of the strategies successfully replicate the periodic breakup of the sheet cavity and the formation of the cloud cavity. The predicted frequency of cavity shedding using compressible methods is higher than that using the incompressible method. In addition, all the CFD simulations confirm that the disturbance moving upward in the sheet cavity is actually a condensation shock. The overpressure resulting from the collapse of the cavity can be captured using three compressible approaches. The boundary layer and time-averaged hydrofoil pressure coefficient are compared and analyzed, revealing a negligible difference among the three compressible simulation results.},

key = {Cavitation, sheet cloud},

keywords = {Cavitation, Cloud cavitation, Sheet Cavitation},

pubstate = {published},

tppubtype = {article}

}

@article{Zhang2024d,

title = {Phase classification and transient effects of the start-up process of multi-functional pump station in pump mode},

author = {Xiaowen Zhang and Giorgio Pavesi and Zhe Xu and Xijie Song and Fangping Tang},

doi = {10.1016/j.est.2024.113517},

issn = {2352152X},

year  = {2024},

date = {2024-01-01},

journal = {Journal of Energy Storage},

volume = {100},

publisher = {Elsevier Ltd},

abstract = {In the context of achieving the goal of carbon neutrality, multi-functional pump stations (MFPS) have been greatly developed as a new energy system in recent years. The MFPS can operate in forward direction in pump mode to pump water and in turbine mode in reverse direction to generate electricity. At present, the instability of the MFPS during start-up process (SUP) in pump mode has become the key to restricting the operating life and further development of MFPS. In this paper, based on the motion characteristics of the pump and the cut-off facility (COF), the SUP of the MFPS in pump mode is clearly classified. In order to reveal the transient effect during the SUP, the steady-state full characteristic experiment (SFCE) of the pump was carried out. The occurrence phase of the transient effect during the SUP is analyzed, and the deviation between the steady-state external characteristics and the transient characteristics is revealed. In this study, the evaluation formula of the start-up completion degree (SUCD) of the MFPS in pump mode is proposed for the first time, and the evaluation and identification of the start-up progress at different phases are completed. The results show that the water flow in the system is in a reverse flow state in the Phase I. The SUCD of Phase I is 17 %. In the Phase II, The high-speed jet flow in the pump flows to the inlet of the guide vane (GV), which gradually changes the mainstream direction in the GV. A certain vortex structure can be observed at the exit of the flap gate (FG). The SUCD of Phase II is 61 %. In the Phase I and II, the dimensionless head of transient simulation is much larger than that of SFCE. In the Phase III, the flow state in the impeller will gradually stabilize. The transient effect disappears and the pressure fluctuation intensity decreases. The SUCD of Phase III is 93 %. In the Phase IV, the separation vortex that persists from Phase I-III at the tail of the GV blades disappears. The diversion capacity at the gate increases, and significant annular flow can be observed near the FG.},

keywords = {Multi-functional pump station, Phase classification, Pump Mode, Start-up process, Steady-state full characteristic experiment, Transient effect},

pubstate = {published},

tppubtype = {article}

}

@article{Zhang2024c,

title = {Unstable flow analysis of transient process in the pump as turbine during turbine mode caused by pump power failure},

author = {Chenying Zhang and Giorgio Pavesi and Ji Pei and Wenjie Wang and Shouqi Yuan and Jiawei Shen},

doi = {10.1063/5.0233491},

issn = {10897666},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

journal = {Physics of Fluids},

volume = {36},

issue = {11},

publisher = {American Institute of Physics},

abstract = {Mixed-flow pump as turbines (PATs) serve as pivotal components within energy micro-grids, facilitating energy conversion and storage. However, the emergence of pressure pulsations in these systems can markedly affect their stability and efficiency, especially in pump power failure. To simulate the power-off transition accurately, the commercial computational fluid dynamics code ANSYS CFX® is integrated by a Fortran program through ANSYS parametric design language in the transient simulation to enable real-time iterative calculations of angular momentum equations for mixed-flow PAT at varying speeds. This study integrates the analysis of radial forces, vortices, and flow lines to elucidate the sudden changes in pressure pulsations observed during the transition stages. Specifically, significant fluctuations in the amplitude of pressure pulsations at the volute tongue were found for various initial flow rates, which correlated closely with changes in radial forces. The sudden increase and nonuniform distribution of radial forces emerged as the main factors of these fluctuations. In addition, the study reveals that the intensity of pressure fluctuations evidenced by wavelet time-frequency analysis on the pressure surface of the blade significantly exceeds that on the back surface of the blade. Furthermore, in the flow characteristics inside the draft tube, the pressure pulsation signals are mainly concentrated in the low-frequency region and are accompanied by the presence of a double-helix structure. These results provide an important reference for further understanding of the operating mechanism of the mixed-flow pump as a turbine, which helps to optimize the design and improve the performance.},

keywords = {PAT, Power Failure, Pump as Turbine, Runaway},

pubstate = {published},

tppubtype = {article}

}

@article{Zhang2024b,

title = {Influence of gate cutoff effect on flow mode conversion and energy dissipation during power-off of prototype tubular pump system},

author = {Xiaowen Zhang and Fangping Tang and Giorgio Pavesi and Chongyang Hu and Xijie Song},

doi = {10.1016/j.energy.2024.132957},

issn = {18736785},

year  = {2024},

date = {2024-01-01},

journal = {Energy},

volume = {308},

publisher = {Elsevier Ltd},

abstract = {Understanding the cutoff effect of gates is essential for enhancing the overall quality of the pump system's power-off process, minimizing energy losses, and reducing potential risks associated with hydraulic transients. In this study, both numerical simulations and experimental investigations were conducted on the power-off process of a tubular pump system, considering scenarios with and without gate functionality. The simulations utilized a dynamic mesh method to model gate movement, incorporated the torque balance equation to determine the real-time impeller speed, and applied the 3D-VOF method for free surface modeling in reservoirs. Power-off experiments were performed on a model pump system and a prototype pump system to validate the numerical simulation results. To elucidate the mechanism of the gate's cutoff effect, flow modes during the power-off process were categorized based on the four-quadrant static test results of the pump, revealing the deviations between transient and static characteristics. By comparing the transient flow structures of the pump system under different gate operating states, specific energy dissipation behaviors during gate cutoff were analyzed. The research findings enhance the understanding of hydraulic transients, which is essential for developing more sustainable and resilient energy systems.},

keywords = {Cut-off effect, Energy conversion, Flow mode, Large pump systems, Power-off process, Transient deviations},

pubstate = {published},

tppubtype = {article}

}

@article{Zhang2024,

title = {Research on the mechanism of severe unsteadiness of PAT braking condition during the power failure},

author = {Chenying Zhang and Wenjie Wang and Giorgio Pavesi and Shouqi Yuan and Ji Pei},

doi = {10.1016/j.renene.2024.121019},

issn = {18790682},

year  = {2024},

date = {2024-01-01},

journal = {Renewable Energy},

volume = {232},

publisher = {Elsevier Ltd},

abstract = {The Pump-As-Turbine (PAT) technology has become popular in micro hydropower stations due to its simple installation and cost-effectiveness. Nevertheless, power failures present a substantial risk to the secure and steady functioning of PAT's braking system. The commercial CFD code (ANSYSCFX) is improved by incorporating a secondary development to model the power-off transition using Fortran accurately. This enhancement allows for real-time iterative calculations of angular momentum equations for mixed-flow PAT at different speeds. Meanwhile, the time–frequency domain analysis is utilized to analyze pressure pulsation signals and the evolution of the internal flow field in mixed-flow PAT. An investigation was conducted to have a deeper understanding of braking circumstances. The results revealed that the main frequency of the pressure pulsation aligns with the blade frequency at various flow rates, and there is a sudden change in pressure amplitude during the braking phase. The impeller experienced the majority of energy losses, with the draft tube being the subsequent area of concern. In addition, a thorough examination and comparison of the changes in the internal flow field during braking were carried out. This analysis revealed a distinct double helix structure within the draft tube, with a slower inner helix and a faster outer helix. Furthermore, it was observed that there is a strong correlation between wall shear stresses and hydraulic losses on the blade surface. This research enhanced understanding of the flow characteristics of mixed-flow PAT can help improve system safety and provide valuable guidance for future optimization efforts.},

keywords = {Braking conditions, CFD numerical simulation, Energy loss, Pump as Turbine, Transient characteristics, Unsteady Flow Evolution},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2024,

title = {Effect of return channel on performance and pressure fluctuation of pump turbine},

author = {Wenjie Wang and Gai Qiu and Ji Pei and Giorgio Pavesi and Geyuan Tai and Shouqi Yuan},

doi = {10.1063/5.0229130},

issn = {10897666},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

journal = {Physics of Fluids},

volume = {36},

issue = {10},

publisher = {American Institute of Physics},

abstract = {To stabilize the operation of pumped storage power station, an orthogonal experimental design was proposed to optimize the return channel with the splitter blades of the pump turbine. The calculation results of various return channel models under multiple operating conditions indicated that inlet distance a1 and blade number z considerably affect the efficiency and flow pattern in the flow passage. The optimal scheme improved efficiency by nearly 3% at 0.6Qd. The Savitzky-Golay filtering method and Fast Fourier Transform were used to analyze the unsteady characteristics of the pump turbine in pump model. The amplitude of pressure pulsations at the blade passing frequency in the vaneless space and the interference zone between the guide vane and return channel reduced considerably, and the pressure pulsation amplitude in the vaneless zone decreased by 50%, 48%, and 20% for 0.6Qd, 1.0Qd, and 1.1Qd operating conditions. A Continuous Wavelet Transform was used to analyze frequency signals during the shutdown transition process. The optimization of the splitter blades improved the flow pattern in their corresponding flow passages and suppressed high-amplitude pressure pulsations in the unit for the stable operation of the pumped storage power station.},

keywords = {Closure of Wicket Gate, Guide Vane Closure, Hydro plant control, Pumped hydro storage},

pubstate = {published},

tppubtype = {article}

}

@article{Zhou2023,

title = {Effects of duct profile parameters on flow characteristics of pump-jet: A numerical analysis on accelerating and decelerating ducts distinguished by cambers and angles of attack},

author = {Yunkai Zhou and Giorgio Pavesi and Jianping Yuan and Yanxia Fu and Quanlin Gao},

doi = {10.1016/j.oceaneng.2023.114733},

issn = {00298018},

year  = {2023},

date = {2023-01-01},

journal = {Ocean Engineering},

volume = {281},

publisher = {Elsevier Ltd},

abstract = {The aim of this study is to investigate the effects of duct profile parameters cambers and angles of attack that distinguish accelerating and decelerating ducts on the flow characteristics of pump-jet. A detailed numerical analysis is carried out to compare the properties of pump-jets with different cambers and attack angles, and to explore the mutual interaction between the duct and components of pump-jet. Beforehand, the numerical methodology is validated by comparing the experiment and simulation results of the pump-jet under mooring conditions and propeller VP1304. Five cambers (f = 0.5t, 0.25t, 0, −0.25t, −0.5t) and three attack angles (α = 4°, 0°, −4°) of duct profile are considered carefully to distinguish accelerating and decelerating ducts, focusing on the propulsion performance and flow field information. The results show that the flow velocity at the outlet of the accelerating ducts is significantly higher compared to the inlet velocity, as opposed to the phenomenon produced by decelerating ducts. The variation of camber makes the internal evolution of the flow field more intuitive compared with the change of angles of attack. Further results indicate that the maximum efficiency of pump-jet drops after the modest growth as the cambers decrease, whose location shifts towards the lower advance coefficient J. The alteration of α leads to making the trend more direct and apparent for the decelerating and accelerating ducts. The high f is advantageous for the cavitation resistance of inside components, like rotor blades and stator blades. The impacts of changing α on the distribution of pressure in pump-jets with accelerating and decelerating ducts are more prominent than changing f. Moreover, the effects of both variations of f and α on the circumferential distributions of the velocity components are prominent, while there are still significant differences between these changes. Additionally, the velocity distribution at the inlet of pump-jets with decelerating ducts is higher than that at the outlet, and the velocity distribution of pump-jets with accelerating ducts presents the opposite pattern.},

keywords = {Duct profile parameters, Flow characteristics, Hydrodynamic performance, Numerical simulation, Pump-jet},

pubstate = {published},

tppubtype = {article}

}

@article{Yan2023,

title = {Flow State at Impeller Inlet: Optimization of Conical Frustum Section of Elbow Inlet Conduit in Large Low-Lift Pump Station},

author = {Tianxu Yan and Baoyun Qiu and Jianping Yuan and Giorgio Pavesi and Fangling Zhao and Huijie Wang},

doi = {10.1115/1.4056452},

issn = {0098-2202},

year  = {2023},

date = {2023-01-01},

urldate = {2023-01-01},

journal = {Journal of Fluids Engineering},

volume = {145},

issue = {4},

publisher = {ASME International},

abstract = {In large low-lift pump stations, the pump assembly comprises an inlet conduit, a pump, and an outlet conduit. A short conical frustum section that connects the elbow section with the impeller inlet directly affects the impeller inflow state, thereby influencing the overall performance. Therefore, investigating the conical frustum section contributes to studying the effect of inflow states on the performances of pump assemblies and similar pumping systems. To improve the pump assembly efficiency, three parameters of the conical frustum section, i.e., the contraction angle, height, and centerline inclination angle, are investigated and optimized via univariate and multivariate analyses. The flow field and external characteristics of the pump assembly are investigated via computational fluid dynamics simulation with a constant head. Furthermore, a comprehensive analysis and discussion of the performance improvement mechanisms are presented. The results indicate that the axial velocity distribution at the impeller inlet conforming to the cascade high-efficiency characteristics will achieve a better pump performance compared with a uniform distribution. The pump efficiency distribution can be predicted and visualized based on the cascade efficiency characteristics and the flow state at the impeller inlet using a machine learning method. In addition, the directions and distribution of the lateral and axial components of the inflow velocities have great impacts on the circulation distribution. A sensible circulation distribution at the guide vane outlet can suppress the entropy production and reduce hydraulic loss of the outlet conduit. In this case, a significant increase in the pump assembly efficiency is obtained.},

keywords = {Impeller Inlet, Pump, Pump Station},

pubstate = {published},

tppubtype = {article}

}

@article{YinPavesi2023-01,

title = {Revisiting RANS prediction of transitional flow on T3A flat plate subject to various freestream turbulences},

author = {Tingyun Yin and Giorgio Pavesi and Shouqi Yuan},

url = {https://linkinghub.elsevier.com/retrieve/pii/S004579302300035X},

doi = {10.1016/j.compfluid.2023.105810},

issn = {00457930},

year  = {2023},

date = {2023-01-01},

journal = {Computers & Fluids},

volume = {254},

pages = {105810},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Zanetti2023b,

title = {Effect of the von Karman Shedding Frequency on the Hydrodynamics of a Francis Turbine Operating at Nominal Load},

author = {Giacomo Zanetti and Giovanna Cavazzini and Alberto Santolin},

url = {https://www.mdpi.com/2504-186X/8/3/27/htm https://www.mdpi.com/2504-186X/8/3/27},

doi = {10.3390/IJTPP8030027},

issn = {2504-186X},

year  = {2023},

date = {2023-01-01},

journal = {International Journal of Turbomachinery, Propulsion and Power 2023, Vol. 8, Page 27},

volume = {8},

issue = {3},

pages = {27},

publisher = {Multidisciplinary Digital Publishing Institute},

abstract = {This paper presents a numerical analysis of the influence of the von Karman vortex shedding at the blade trailing edge on the hydrodynamics of a recently installed small hydro Francis turbine manifesting very loud and high-frequency acoustic pulsations when operating close to the nominal load. A reduced single-passage numerical model is developed to reduce the computational effort of the simulation while ensuring high accuracy in the assessment of fluid flow. The accuracy of the proposed numerical approach is investigated by comparing the frequency spectrum of the experimentally acquired acoustic frequency and the numerical pressure signals, confirming the nature of the machine’s vibrations. The validated numerical model represents a useful tool for an in-depth analysis of the machine’s hydrodynamics in the preliminary design phases. The proposed approach represents a valid alternative to the traditional correlation-based approach for the evaluation of the von Karman shedding frequency with less computational effort compared with a transient simulation of the entire machine.},

keywords = {Francis Turbine, Interblade vortex, mechanical resonance, von Karman vortices},

pubstate = {published},

tppubtype = {article}

}

@article{Casarin2023,

title = {Battery and Flywheel hybridization of a reversible Pumped-Storage Hydro Power Plant for wear and tear reduction},

author = {Stefano Casarin and Giovanna Cavazzini and Juan Ignacio Pérez-Díaz},

url = {https://doi.org/10.1016/j.est.2023.108059},

doi = {10.1016/j.est.2023.108059},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Energy Storage},

volume = {71},

pages = {108059},

abstract = {Energy security and environmental challenges are some of the drivers for increasing the electricity generation from non-programmable Renewable Energy Sources (RES), adding pressure to the grid, especially if located in weakly connected (or isolated) islands, like Sardinia. Variable-speed Pumped Storage Hydro Power (PSHP) can offer a high degree of flexibility in providing ancillary services (namely primary and secondary regulations), but due to the hydro-mechanical nature of the equipment, sudden variations in the power output cause wear and tear. Other energy storage devices cannot compete with PSHP in terms of energy and power availability. The aim of this research is to assess the benefits derived from the hybridization of a PSHP with Battery Energy Storage System (BESS) and Flywheel Energy Storage System (FESS), to be installed in the Sardinia island (Italy). A dynamic model of the hybrid plant was made in MATLAB-Simulink ® environment. A detailed model of the variable-speed pump-turbine was obtained from experimental data, and a simplified model of a fixed-speed turbine was produced. A detailed FESS model was provided by CIEMAT (Madrid, Spain) and a simplified BESS model was included. A dedicated control strategy to manage the power flows and accounting for State Of Charge (SOC) control, was implemented. A total of 100 combinations of BESS and FESS powers were taken into account, and the control strategy was calibrated for each one of them. The plant was simulated open-loop over a 3600 s time period, feeding historical frequency and Automatic Generation Control (AGC) data. The simulations covered three PSHP operation modes: variable/fixed-speed turbine and variable-speed pump, and with/without hybridization. The performances of the hybridization were evaluated with wear and tear indicators for the PSHP (distance travelled by and number of movements of the wicket gate for turbine, fluctuations of the shaft torque for the pump) and capacity loss (life consumption) for the BESS. The results show that all the combinations of BESS and FESS powers result in the reduction of both the travelled distance and number of movements of the guide vanes. The best hybrid combination for the PSHP does not affect the BESS life consumption, which still is always in an acceptable range. A comparison between the non-hybrid variable-speed turbine and the hybrid fixed-speed counterpart shows that the electric powers do not differ substantially, but the hybridization smooths the movement of the guide vanes. The pump torque fluctuations sharply decrease with the hybridization, but more research is needed to validate that the change in the fluctuation index corresponds to a physical phenomenon. Overall, the hybridization improves the plant performances in terms of wear and tear reduction, and the presence of an additional FESS benefits both the BESS and the PSHP. The results also highlight the necessity for more research in variable-speed pumps providing ancillary services, and their impact.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Cavazzini2023,

title = {Residential Buildings Heating and Cooling Systems: The Key Role of Monitoring Systems and Real-Time Analysis in the Detection of Failures and Management Strategy Optimization},

author = {Giovanna Cavazzini and Alberto Benato},

url = {https://www.mdpi.com/2227-9717/11/5/1365},

doi = {10.3390/pr11051365},

issn = {2227-9717},

year  = {2023},

date = {2023-01-01},

journal = {Processes},

volume = {11},

issue = {5},

pages = {1365},

abstract = {<p>Nineteen percent of global final energy consumption is used to generate electricity and heat in buildings. Therefore, it is undisputed that the building sector needs to cut consumption. However, this reduction needs to be driven by data analysis from real building operations. Starting from this concept and with the aim of proving the benefits deriving from the installation of a monitoring system in a real operating environment, in this work a monitoring system has been installed to monitor the centralised heating and cooling system of a residential building composed of 57 residential units. The data acquired from the installed sensors are collected and subsequently analysed in an ad hoc tool to detect anomalies, performance decay, malfunctions, and failures of the machines, as well as to understand if the implemented management strategy is appropriate in terms of energy and cost savings. The results show the key role of the data acquired by the monitoring system and analysed by the developed tool in terms of ability to detect failures and malfunctions in both the heating and cooling modes, as well as to help both in finding the proper management strategy and in identifying the performance deviation precursors of machine failure.</p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Zanetti2023,

title = {Three-dimensional evolution of the flow unsteadiness in the S-shape of pump-turbines and its correlation with the runner geometry},

author = {Giacomo Zanetti and Giovanna Cavazzini and Alberto Santolin},

url = {https://doi.org/10.1016/j.est.2022.106176},

doi = {10.1016/j.est.2022.106176},

issn = {2352152X},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Energy Storage},

volume = {57},

issue = {September 2022},

pages = {106176},

publisher = {Elsevier Ltd},

abstract = {Pump-turbines (RTP) are the most common mechanical equipment adopted in pumped-hydro power plants and, for grid balancing purposes, are required to sharply switch from pumping to generating mode, and to extend their operative, jeopardizing not only the machine operability but also its life. New design approaches to avoid the onset of unstable behaviours are still far from being defined, and control strategies for accelerating start-up/shut-down procedures are still not effective since these are based on semi-empirical approaches, due to the lack of identification of precursors of the unstable behavior. In this paper, a numerical analysis of the unstable behavior of an RPT during the transition from partial load up to the turbine-brake area was carried out. The fluid-dynamics in different operating points (partial load, run-away condition, turbine brake) was deeply investigated, identifying the rotor-stator mechanisms causing the 3D evolution of the flow field leading to the development of the unstable behavior. Three evolution phases (inception, growth and consolidation) were identified and clearly correlated with the runner geometry and with the S-Shape of the RPT characteristic curve. Customized signal processing strategies were adopted for spectrally characterizing each phase so as to identify potential triggers for new monitoring and control strategies. Moreover, for the first time, a clear fluid-dynamic explanation of the empirical results found in literature on the influence of the runner geometry is provided.},

keywords = {Interblade vortex, Pump as Turbine, Pumped-hydropower, Rotating Stall, S-shape},

pubstate = {published},

tppubtype = {article}

}

@article{YinPavesi2022-01,

title = {Dynamic responses of pitching hydrofoil in laminar–turbulent transition regime},

author = {Tingyun Yin and Giorgio Pavesi},

doi = {10.1016/j.jfluidstructs.2022.103544},

issn = {10958622},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Fluids and Structures},

volume = {111},

publisher = {Academic Press},

abstract = {Recently, the problem of a transitional boundary layer around a pitching foil has been attracting increasing attention. To determine the underlying physical mechanisms, in this study, a pitching hydrofoil is numerically investigated using the shear stress transport (SST) k–ω turbulence model coupled with the γ–Re˜θt transition model. First, the prediction of the static performance is compared with the experimental measurements and XFOIL data to validate and verify the numerical accuracy of the proposed method. Subsequently, the flow morphologies induced by sinusoidal and non-sinusoidal pitching laws are analyzed and compared in different reduced frequencies. The results indicate that reducing the empirical coefficient, A1, in the SST k–ω turbulence model can generate the flow separation in advance, thus improving the prediction of the hydraulic performance at a high angle of attack. The dynamic behavior of the laminar separation bubble is strongly associated with the pitching method and velocity. The collapse of the laminar separation bubble can destabilize the local boundary layer, generating multi-laminar separation bubbles. When new separation bubbles form and shed, a turbulent boundary layer moves downstream and is adsorbed on the surface simultaneously. The turbulence flow passes through the trailing edge, destroying the local vortex, contributing to a transiently elevated hydrodynamic lift. During a rapid pitching down, a counterclockwise trailing edge vortex becomes increasingly unstable, repeating the processes of inception, development, and shedding. The Theodorsen model fails to produce a reasonable hysteresis loop owing to the assumption of a fully attached flow. The results of a hybrid of the Theodorsen and Øye models show noticeable improvement in the dynamic lift prediction. The empirical coefficient, ks, of the Snel model is optimized, improving the predictions of low-frequency pitching significantly. All dynamic stall models present the same trend: low-frequency motions show better agreement than high-frequency ones. In the former, modeling of a non-sinusoidal pitching is closer to the transient numerical results than that of a sinusoidal motion.},

keywords = {Dynamic stall model, Laminar separation bubble, Laminar–turbulent transition, Pitching Hydrofoil},

pubstate = {published},

tppubtype = {article}

}

@article{Zhou2022,

title = {A Review on Hydrodynamic Performance and Design of Pump-Jet: Advances, Challenges and Prospects},

author = {Yunkai Zhou and Giorgio Pavesi and Jianping Yuan and Yanxia Fu},

url = {https://www.mdpi.com/2077-1312/10/10/1514},

doi = {10.3390/jmse10101514},

issn = {20771312},

year  = {2022},

date = {2022-01-01},

urldate = {2022-01-01},

journal = {Journal of Marine Science and Engineering},

volume = {10},

issue = {10},

publisher = {MDPI},

abstract = {A pump-jet, which is generally and widely adopted on underwater vehicles for applications from deep sea exploration to mine clearing, consists of a rotor, stator, and duct, with the properties of high critical speed, high propulsion efficiency, great anti-cavitation performance, and low radiated noise. The complex interaction of the flow field between the various components and the high degree of coupling with the appendage result in the requirements of in-depth research on the hydrodynamic performance and flow field for application and design. Due to the initial application on the military field and complicated structure, there is scant literature in the evaluation of pump-jet performance and optimal design. This paper, in a comprehensive and specialized way, summarizes the pump-jet hydrodynamic performance, noise performance, and flow field characteristics involving cavitation erosion and vortices properties of tip-clearance, the interaction between the rotor and the stator and the wake field, as well as the optimal design of the pump-jet. The merits and applications range of numerical and experimental methods are overviewed as well as the design method. It also concludes the main challenges faced in practical applications and proposes a vision for future research. It was found that the compact structure and complex internal and external flow field make the pump-jet significantly different, also leading to higher performance. As the focus of cavitation research, vortices interact with the complex structure of the pump-jet, leading to instabilities of the flow field, such as vibration, radiated noise, and cavitation erosion. The effective approaches are adopted to reduce radiated pump-jet with minimal influence on the hydrodynamic performance, such as eliminating the tip clearance and installing the sawtooth duct. Advanced optimal technology can achieve high performance, cavitation performance, and acoustic performance, possessing good prospects. Further developments in investigation and the application of pump-jets in the multidisciplinary integration of fluid dynamics, acoustics, materials, chemistry, and bionics should be the main focus in future research.},

keywords = {design, Flow field, Hydrodynamic performance, Pump-jet},

pubstate = {published},

tppubtype = {article}

}

@article{GanPavesi2022-01,

title = {Application of intelligent methods in energy efficiency enhancement of pump system: A review},

author = {Xingcheng Gan and Ji Pei and Giorgio Pavesi and Shouqi Yuan and Wenjie Wang},

doi = {10.1016/j.egyr.2022.09.016},

issn = {23524847},

year  = {2022},

date = {2022-01-01},

urldate = {2022-01-01},

journal = {Energy Reports},

volume = {8},

pages = {11592-11606},

publisher = {Elsevier Ltd},

abstract = {Energy consumption around the world is growing at an alarming rate. That brings enormous pressure on energy production and environmental issues. Nowadays, energy efficiency enhancement strategies are considered the crucial approaches to release this problem. The pumps accounts for nearly 21% of the world electricity consumption of industrial motor-driven systems. Hence, much research focused on improving the energy efficiency of the pumps and their systems. According to the works of literature, the level of design of pumps for most applications is already extremely high while the system performance could be further improved by regulations, and the average energy savings potential achievable through pump system adjustments is about 30%. This paper focuses on the advanced characteristic modeling methods, and energy efficiency enhancement regulation approaches for the parallel pumping system. A comprehensive summary of traditional scheduling methods and advanced regulation methods based on computational intelligence has been made to provide insight for future research.},

keywords = {Energy efficiency enhancement, Energy-efficient control, Inline pump, Intelligent method, Optimization, Pump system},

pubstate = {published},

tppubtype = {article}

}

@article{YinPavesi2022-02,

title = {Numerical investigation on the inhibition mechanisms of unsteady cavitating flow around stepped hydrofoils},

author = {Tingyun Yin and Giorgio Pavesi and Ji Pei and Shouqi Yuan},

doi = {10.1016/j.oceaneng.2022.112540},

issn = {00298018},

year  = {2022},

date = {2022-01-01},

journal = {Ocean Engineering},

volume = {265},

issue = {August},

publisher = {Elsevier Ltd},

abstract = {In this work, the influence of obstacles on the control of unsteady cavitating flows is investigated numerically within the framework of homogeneous flow. The predicted Strouhal number of the cavity shedding around the smooth hydrofoil is close to the experimental value, indicating the accuracy of the numerical simulation. Four installation sites are examined, including 10%, 20%, 30%, and 40% of the chord length from the leading edge. The instantaneous and time-averaged hydrodynamics in conjunction with the unsteady cavity behaviors are discussed in detail. The results indicate that all cases display similar flow patterns within one shedding cycle, including the development of the attached sheet cavity, sheet/cloud transformation, and cloud cavity collapse. The hydraulic lift is governed by the partial cavity oscillation but could be significantly modified by the trailing wake vortices, especially after installing the obstacle. The recommended optimal position of the obstacle is X/L=0.4, and the corresponding pressure fluctuations and lift-to-drag ratio achieve the best performance. However, the mean vapor volume is significantly reduced when the obstacle is located at X/L=0.3, indicating the minimum risk of cavitation erosion. Installing the obstacle at different locations along the suction surface will provide different effects on oscillation based on the analyses of the Lagrangian coherent structures. The corresponding primary frequency varies in a narrow range between 106.67 Hz ∼ 121.33 Hz. Proper orthogonal decomposition (POD) analyses of the vapor fraction reveal the contribution of flow morphology to the partial cavity oscillation. Installing the obstacle could significantly limit the size of each pattern, especially for X/L=0.4.},

keywords = {Backward finite-time Lyapunov exponents, Partial cavity oscillation, Passive suppression, Proper orthogonal decomposition, Spatial–temporal behaviors},

pubstate = {published},

tppubtype = {article}

}

@article{YinPavesi2022-03,

title = {Large eddy simulation of cloud cavitation and wake vortex cavitation around a trailing-truncated hydrofoil},

author = {Ting Yin and Giorgio Pavesi and Ji Pei and Shou Yuan and Xing Gan},

doi = {10.1007/s42241-022-0073-9},

issn = {18780342},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Hydrodynamics},

volume = {34},

issue = {5},

pages = {893-903},

publisher = {Springer},

abstract = {The cavitation has received considerable attention for decades because of its negative influence on the performance and the safety of the hydraulic machinery. In this study, a large eddy simulation is carried out to numerically investigate the unsteady cavitating flow around a trailing-truncated NACA 0009 hydrofoil for determining the underlying physical mechanisms. Two types of cavitation morphologies are identified: The large-scale bubble cluster and the von Kármán vortex cavity, named as the cloud cavitation and the wake vortex cavitation, respectively. It is shown that the velocity profiles obtained over the hydrofoil suction surface are in good agreement with the experimental data, indicating the accuracy of the current simulation. The dynamic evolution of the sheet/cloud cavity is also well reproduced, covering the sheet cavity breakup, the sheet/cloud transformation, and the collapse of the cloudy bubble cluster. The wake-vortex cavitation is caused by the blunt geometry at the hydrofoil trailing edge, where pairs of vortex cavities are induced. Both the cloud and vortex cavities significantly affect the lift oscillation, which makes it difficult to decompose the components. The fundamental shedding mechanisms of the wake vortex cavitation are discussed based on the finite-time Lyapunov exponent field. Specifically, the suction-side bubble grows and squeezes the giant pressure bubble away from the trailing edge. After the pressure bubble detaches, a new counterclockwise vortex or a new bubble appears at the pressure side, thus lifting the ridge towards the suction trailing edge and generating a strong vortex eye that pinches off the trailing portion of the suction-side bubble.},

keywords = {Cloud cavitation, large eddy simulation, trailing-truncated hydrofoil, wake vortex cavitation},

pubstate = {published},

tppubtype = {article}

}

@article{Pumpturbine,

title = {Numerical investigation of the effect of the closure law of wicket gates on the transient characteristics of pump-turbine in pump mode},

author = {Wenjie Wang and Geyuan Tai and Ji Pei and Giorgio Pavesi and Shouqi Yuan},

url = {https://linkinghub.elsevier.com/retrieve/pii/S0960148122007807 https://www.sciencedirect.com/science/article/pii/S0960148122007807},

doi = {10.1016/j.renene.2022.05.129},

issn = {18790682},

year  = {2022},

date = {2022-01-01},

journal = {Renewable Energy},

volume = {194},

pages = {719-733},

publisher = {Elsevier Ltd},

keywords = {Continuous Wavelet Transform, Detached Eddy simulation, Pressure pulsation, Pump as Turbine, Shutdown process, Wicket gates closure law},

pubstate = {published},

tppubtype = {article}

}

@article{GanPavesi2022-02,

title = {Parametric investigation and energy efficiency optimization of the curved inlet pipe with induced vane of an inline pump},

author = {Xingcheng Gan and Giorgio Pavesi and Ji Pei and Shouqi Yuan and Wenjie Wang and Tingyun Yin},

url = {https://www.sciencedirect.com/science/article/pii/S0360544221030735},

doi = {10.1016/j.energy.2021.122824},

issn = {03605442},

year  = {2022},

date = {2022-01-01},

urldate = {2022-01-01},

journal = {Energy},

volume = {240},

publisher = {Elsevier Ltd},

abstract = {The world energy consumption is currently growing at an alarming rate to support the increase of the world economy and population, which has brought a host of environmental issues. Improving energy efficiency is considered as the crucial solution for changing this situation. The widespread use of inline pumps in the water supply consumes a large amount of electricity, while the efficiency of such devices is lower than the average level. This research is aimed to study the relationship between the shape of the curved inlet pipe and the energy loss distributions by using flow loss visualization technology and correlation analysis. An induced vane was placed at the end of the inlet pipe to suppress the flow phenomena that cause efficiency losses. 700 designs of the inlet pipe with induced vane were generated and calculated to support the research using the automatic simulation approach. An optimization work was also presented to improve the comprehensive performance of the inline pump by using the multi-layer feed-forward neural network and multi-objective particle swarm optimization. An excellent performance improvement was found after the optimization, and a deep analysis of four different design schemes based on the loss visualization method was presented to figure out the main reasons for hydraulic losses in the curved inlet pipe.},

keywords = {Correlation analysis, Energy efficiency enhancement, Flow loss visualization, Inline pump, Multi-objective optimization, Parametric investigation},

pubstate = {published},

tppubtype = {article}

}

@article{Cavazzini2022,

title = {Characterization of the hydrodynamic instabilities in a pump-turbine operating at part load in turbine mode},

author = {Giovanna Cavazzini and Giacomo Zanetti and Alberto Santolin and Guido Ardizzon},

url = {https://iopscience.iop.org/article/10.1088/1755-1315/1079/1/012033},

doi = {10.1088/1755-1315/1079/1/012033},

issn = {1755-1307},

year  = {2022},

date = {2022-01-01},

urldate = {2022-01-01},

journal = {IOP Conference Series: Earth and Environmental Science},

volume = {1079},

issue = {1},

pages = {012033},

publisher = {Institute of Physics},

abstract = {<p>Pump-turbines (RPT) nowadays represents the most common mechanical equipment adopted in the new generation of storage hydro plant. In order to balance the frequent changes in electricity production and consumption caused by unpredictable renewable energy sources, RPT are forced to rapidly switch between the pumping and generating mode also extending their operation under off-design conditions in unstable operating areas. Because of the design criterion adopted for the development of a RPT, an unstable behavior represented by a typical S-shaped profile with a positive slope in the machine’s characteristic can occur near to the runaway condition.</p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Nanoparticles2022,

title = {Optimization of the Adsorption / Desorption Contribution from},

author = {Giovanna Cavazzini and Serena Bari},

year  = {2022},

date = {2022-01-01},

urldate = {2022-01-01},

abstract = {The efficient recovery of low temperature waste heat, representing from 25% up to 55% of the energy losses in industrial processes, still remains a challenge and even Organic Rankine Cycles (ORCs) experience a strong efficiency decay in such a low temperature operating range (T < 150 C). In similar heat transfer processes, several nanofluids have been proposed as a solution for increasing heat transfer efficiency, but they produced only moderate enhancements of the heat transfer efficiency in comparison with pure fluids. This paper aims at numerically assessing the potential gain in efficiency deriving from the application of an unconventional type of nanoparticles, the metal-organic heat carriers (MOHCs), in the ORC field. In comparison with standard nanoparticles, these MOHCs make it possible to extract additional heat from the endothermic enthalpy of desorption, with a theoretically high potential for boosting the heat transfer capacity of ORC systems. In this paper a numerical model was developed and customized for considering the adsorption/desorption processes of the pure fluid R245fa (pentafluoropropane) combined with a crystal structure for porous chromium terephthalate (MIL101). The R245fa/MIL101 nanofluid behavior was experimentally characterized, defining proper semi-emipirical correlations. Then, an optimization procedure was developed, combining the numerical model with a PSO algorithm, to optimize the thermodynamic conditions in the ORC so as to maximize the contribution of desorption/absorption processes. The results confirm the increase in net power output (+2.9% for 100 C) and in expander efficiency (+2.4% for 100 C) at very low heat source temperature. The relevance of tuning the operating cycle and the nanofluid properties is also demonstrated.},

keywords = {adsorption, metal-organic heat carriers, ORC, two-phase fluid, waste heat},

pubstate = {published},

tppubtype = {article}

}

@article{vanDijk2022,

title = {Optimizing Conduit Hydropower Potential by Determining Pareto-Optimal Trade-Off Curve},

author = {Marco Dijk and Stefanus Johannes Vuuren and Giovanna Cavazzini and Chantel Monica Niebuhr and Alberto Santolin},

doi = {10.3390/su14137876},

issn = {20711050},

year  = {2022},

date = {2022-01-01},

journal = {Sustainability (Switzerland)},

volume = {14},

issue = {13},

abstract = {In numerous locations of bulk water supply/distribution systems, energy is dissipated by pressure-reducing devices, whereas it could be recovered by means of turbines or pumps as turbines. These pipe systems, owned and operated by municipalities, water utilities, large water-consuming industries, and mines, could be used as a source of renewable sustainable energy. However, the exploitation of these systems presents several issues related to the complexity of the operational optimization of the hydropower generation facilities and to the potential negative impact on the reliability of the system itself. We have developed a novel procedure to optimize the energy generation in such a conduit system by assessing the interrelationship of storage volumes, demand patterns, operating cycles, and electricity tariff structures. The procedure is a multi-objective genetic algorithm designed to provide a solution to maximize electricity generation and thus revenue and to minimize the risk involved in supplying the demand. A Pareto-optimal trade-off curve is set up, indicating the potential benefit (revenue) versus the reliability index (supply security). The results indicate that a Pareto-optimal trade-off curve was generated from which a solution could be selected which would improve the weekly revenue by up to 7.5%, while still providing a reliable water supply system.},

keywords = {conduit hydropower, energy recovery, Genetic Algorithm, optimized energy generation, pareto optimality, renewable energy},

pubstate = {published},

tppubtype = {article}

}

@article{Yin2021c,

title = {Lagrangian Analysis of Unsteady Partial Cavitating Flow Around a Three-Dimensional Hydrofoil},

author = {Tingyun Yin and Giorgio Pavesi and Ji Pei and Shouqi Yuan and Giovanna Cavazzini and Guido Ardizzon},

url = {https://asmedigitalcollection.asme.org/fluidsengineering/article/143/4/041202/1091940/Lagrangian-Analysis-of-Unsteady-Partial-Cavitating},

doi = {10.1115/1.4049242},

issn = {0098-2202},

year  = {2021},

date = {2021-01-01},

journal = {Journal of Fluids Engineering},

volume = {143},

issue = {4 - April},

pages = {1-11},

publisher = {American Society of Mechanical Engineers (ASME)},

abstract = {This study employs an incompressible homogeneous flow framework with a transport-equation-based cavitation model and shear stress transport turbulence model to successfully reproduce the unsteady cavitating flow around a three-dimensional hydrofoil. Cavity growth, development, and break-off during the periodic shedding process are adequately reproduced and match experimental observations. The predicted shedding frequency is very close to the experimental value of 23 ms. By monitoring the motions of the seeding trackers, growth-up of attached cavity and dynamic evolution of U-type cavity are clearly displayed, which indicating the trackers could serve as an effective tool to visualize the cavitating field. Repelling Lagrangian Coherent Structure (RLCS) is so complex that abundant flow patterns are highlighted, reflecting the intricacy of cavity development. The formation of cloud cavities is clearly characterized by the Attracting Lagrangian Coherent Structure (ALCS), where bumbling wave wrapping the whole shedding cavities indicates the rotating transform of cavities and stretching of the wave eyes shows the distortion of vortices. Generation of the re-entrant jet is considered to be not only associated with the adverse pressure gradient due to the positive attack angle, but also the contribution of cloud cavitating flow, based on the observation of a buffer zone between the attached and cloud cavities.},

keywords = {Lagrangian Analysis, Shedding frequencies, Three-dimensional Hydrofoil, Unsteady Cavitating Flow},

pubstate = {published},

tppubtype = {article}

}

@article{Cavazzini2021c,

title = {Techno-economic benefits deriving from optimal scheduling of a Virtual Power Plant: Pumped hydro combined with wind farms},

author = {Giovanna Cavazzini and Alberto Benato and Giorgio Pavesi and Guido Ardizzon},

url = {https://www.sciencedirect.com/science/article/pii/S2352152X21002103 https://doi.org/10.1016/j.est.2021.102461},

doi = {10.1016/J.EST.2021.102461},

issn = {2352-152X},

year  = {2021},

date = {2021-01-01},

urldate = {2021-01-01},

journal = {Journal of Energy Storage},

volume = {37},

issue = {May 2020},

pages = {102461},

publisher = {Elsevier Ltd},

abstract = {Wind and solar are renewable sources characterized by a great potential but a variable and unpredictable nature. Characteristics that provoke mismatch between power supply and demand which in turns are the source of network control issues. Problems manageable with the installation of large-scale energy storage like Pumped Hydro Energy Storage (PHES). To this purpose, the paper presents a techno-economic analysis for assessing the benefits deriving from the hybridization of a seawater PHES (sPHES) plant with an in-operation wind farm. Plants work as a Virtual Power Plant (VPP) instead of two separate unit. The hybridization aims to avoid the unbalances of the wind farm, having negative impact on both the grid and the wind farm owner itself. The unbalances cause unpredictable deviations from the predicted production and, hence, power production fluctuations faced by the grid with curtailments and/or calls in operation of fossil-fuelled power plants. A VPP techno-economic optimization on a daily bases is performed using the ASD-PSO algorithm while the optimization aim is the revenue maximization. Results show that a VPP composed by a sPHES and a wind farm and with a single owner, is able to manage the wind farm production, improving the revenue of 6.8% compared to plants acting separately on the market. The VPP approach is also convenient in the case of a joint venture between the plants owners. But, in this case, the revenue is increased only of 0.4% compared to plants working separately. Finally, results also highlight that, in the Italian electricity market, a sPHES plant alone is not able to generate sufficient revenue to guarantee a reasonable payback time while coupling it with a wind farm increases incomes and working days and avoid cost and grid issues in managing the unpredictable wind farm production.},

keywords = {Pumped hydro storage, Renewable integration, Virtual Power Plant, Wind, Wind energy, Wind-hydro integration},

pubstate = {published},

tppubtype = {article}

}

@article{Yin2021b,

title = {Numerical analysis of unsteady cloud cavitating flow around a 3D Clark-Y hydrofoil considering end-wall effects},

author = {Tingyun Yin and Giorgio Pavesi and Ji Pei and Shouqi Yuan},

url = {https://www.sciencedirect.com/science/article/pii/S0029801820312762?utm_campaign=STMJ_AUTH_SERV_PUBLISHED&utm_medium=email&utm_acid=30163317&SIS_ID=&dgcid=STMJ_AUTH_SERV_PUBLISHED&CMX_ID=&utm_in=DM110556&utm_source=AC_ https://www.sciencedirect.com/scienc},

doi = {10.1016/j.oceaneng.2020.108369},

issn = {00298018},

year  = {2021},

date = {2021-01-01},

journal = {Ocean Engineering},

volume = {219},

issue = {April 2020},

pages = {103506},

publisher = {Elsevier Ltd},

abstract = {This study employs an incompressible homogeneous flow framework with a transport equation based cavitation model and density corrected Shear Stress Transport (SST) k-ω turbulence model to successfully reproduce the unsteady cavitating flow around a 3D Clark-Y hydrofoil with an end wall. Cavity growth, development, and break-off during the periodic shedding process are adequately reproduced and match experimental observations. The predicted shedding frequency is very close to the experimental value of 43.48 Hz. The existence of an end wall brings about the generation and convection of wall-side cavity. Moreover, large horse-type cavity structure is captured, which agrees with experimental results. Cavities at the closure region easily detach from the main pocket part resulting in a secondary vortical structure. Differences between numerical and experimental lift are observed, however, similar to our previous findings, the experimental lift coefficient appears to correlate with the inverse of the second derivative of the total cavity volume. Based on the analysis of vorticity transportation, compressibility source occupies the highest contribution of vorticity transportation and is significantly higher than other two terms, which serves the promotion effect at the trailing region of growing attached cavity while inhibits the development of vorticity within the leading area.},

keywords = {Three-dimensional Hydrofoil, Transient characteristics, Unsteady Cloud Cavitation},

pubstate = {published},

tppubtype = {article}

}

@article{Yin2021,

title = {Numerical investigation of unsteady cavitation around a twisted hydrofoil},

author = {Tingyun Yin and Giorgio Pavesi and Ji Pei and Shouqi Yuan},

url = {https://doi.org/10.1016/j.ijmultiphaseflow.2020.103506 https://www.sciencedirect.com/science/article/pii/S0301932220306170},

doi = {10.1016/j.ijmultiphaseflow.2020.103506},

issn = {03019322},

year  = {2021},

date = {2021-01-01},

journal = {International Journal of Multiphase Flow},

volume = {135},

pages = {103506},

publisher = {Elsevier Ltd},

abstract = {In this paper, the unsteady cavitating flow around a symmetrical twisted hydrofoil is investigated numerically. Cavitating flow characteristics are analyzed in terms of dynamical behaviors and temporal/spatial fluctuations of the cavities along the hydrofoil. At the midsection of the foil, sheet cavity firstly grows with nearly constant speed until the occurrence of the reverse flow at the closure line. During the reverse phase the flow moves upstream, and the sheet cavity keeps growing turbulently with low vapor content at the closure area. Fast Fourier Transform (FFT), Bispecturm and Dynamic Mode Decomposition (DMD) analyses show the existence of harmonics of the shedding frequency, of which the double and triple frequency are captured but only the fundamental frequency dominates the cavitating field. Pressure fluctuations around the hydrofoil and force coefficients are governed by the acceleration of vapor cavity. Application of Proper Orthogonal Decomposition (POD) displays the large-scale coherent structures among cavity shedding evolution. The sheet cavity growth, the main cavity shrinking and developing into a pair of root-like cavity structure and the sector cavity structure are captured by the first mode.},

keywords = {Dynamical behaviors, Proper orthogonal decomposition, Spectrum Analysis, Temporal/spatial analysis, Unsteady Cavitating Flow},

pubstate = {published},

tppubtype = {article}

}

@article{Cavazzini2021,

title = {Analysis of the Inner Fluid-Dynamics of Scroll Compressors and Comparison between CFD Numerical and Modelling Approaches},

author = {Giovanna Cavazzini and Francesco Giacomel and Alberto Benato and Francesco Nascimben and Guido Ardizzon},

url = {https://www.mdpi.com/1996-1073/14/4/1158},

doi = {10.3390/en14041158},

issn = {1996-1073},

year  = {2021},

date = {2021-01-01},

journal = {Energies},

volume = {14},

issue = {4},

pages = {1158},

abstract = {Scroll compressors are widely adopted machines in both refrigeration systems and heat pumps. However, their efficiency is basically poor and constitutes the main bottleneck for improving the overall system performance. In fact, due to the complex machine fluid dynamics, scroll design is mainly based on theoretical and/or semi-empirical approaches. Designs strategies that do not guarantee an in-depth analysis of the machine behavior can be supplemented with a Computation Fluid Dynamics (CFD) approach. To this purpose, in the present work, the scroll compressor inner fluid dynamics is numerically analyzed in detail using two CFD software and two different modelling strategies for the axial gap. The analysis of the fluid evolution within the scroll wraps reveals unsteady phenomena developing during the suction and discharge phases, amplified by the axial clearance with negative impact on the main fluid flow (e.g., −13% of average mass flow rate for an axial gap of 30 μ) and on the scroll performance (e.g., +26% of average absorbed power for an axial gap of 30 μ). In terms of accuracy, the k-ε offers good performance on the estimation of average quantities but proves to be inadequate for capturing the complexity of the unsteady phenomena caused by the axial gap (e.g., −19% of the absorbed power in case of perfect tip seal). The need for considering specific geometric details in design procedures is highlighted, and guidelines on the choice of the most suitable numerical model are provided depending on the analysis needs.},

keywords = {Axial Gap, CFD Analysis, positive displacement machine, scroll, unsteady phenomena},

pubstate = {published},

tppubtype = {article}

}

@article{Benato2021,

title = {TES-PD: A Fast and Reliable Numerical Model to Predict the Performance of Thermal Reservoir for Electricity Energy Storage Units},

author = {Alberto Benato and Francesco De Vanna and Ennio Gallo and Anna Stoppato and Giovanna Cavazzini},

url = {https://www.mdpi.com/2311-5521/6/7/256},

doi = {10.3390/fluids6070256},

issn = {2311-5521},

year  = {2021},

date = {2021-01-01},

journal = {Fluids},

volume = {6},

issue = {7},

pages = {256},

abstract = {The spread of renewable resources, such as wind and solar, is one of the main drivers to move from a fossil-based to a renewable-based power generation system. However, wind and solar production are difficult to predict; hence, to avoid a mismatch between electricity supply and demand, there is a need for energy storage units. To this end, new storage concepts have been proposed, and one of the most promising is to store electricity in the form of heat in a Thermal Energy Storage reservoir. However, in Thermal Energy Storage based systems, the critical component is the storage tank and, in particular, its mathematical model as this plays a crucial role in the storage unit performance estimation. Although the literature presents three modelling approaches, each of them differs in the considered parameters and in the method of modelling the fluid and the solid properties. Therefore, there is a need to clarify the model differences and the parameter influences on plant performance as well as to develop a more complete model. For this purpose, the present work first aim is to compare the models available in the literature to identify their strengths and weaknesses. Then, considering that the models’ comparison showed the importance of adopting temperature-dependent fluid and storage material properties to better predict the system performance, the authors developed a new and more detailed model, named TES-PD, which works with time and space variable fluid and solid properties. In addition, the authors included the tank heat losses and the solid effective thermal conductivity to improve the model accuracy. Based on the comparisons between the TES-PD model and the ones available in the literature, the proposal can better predict the first cycle charging time, as it avoids a 4% underestimation. This model also avoids overestimation of the delivery time, delivered energy, mean generated power and plant round-trip efficiency. Therefore, the results underline that a differential and time-accurate model, like the TES-PD, even if one-dimensional, allows a fast and effective prediction of the performance of both the tank and the storage plant. This is essential information for the preliminary design of innovative large-scale storage units operating with thermal storage.},

keywords = {Gas turbine thermal storage, Integrated Energy Storage, Numerical modelling, Packed bed},

pubstate = {published},

tppubtype = {article}

}

@article{Stoppato2021,

title = {Environmental impact of energy systems integrated with electrochemical accumulators and powered by renewable energy sources in a life-cycle perspective},

author = {Anna Stoppato and Alberto Benato and Francesco De Vanna},

doi = {10.3390/app11062770},

issn = {20763417},

year  = {2021},

date = {2021-01-01},

journal = {Applied Sciences (Switzerland)},

volume = {11},

issue = {6},

abstract = {The aim of this study is to assess the environmental impact of storage systems integrated with energy plants powered by renewable sources. Stationary storage systems proved to be a valid solution for regulating networks, supporting frequency, and managing peaks in electricity supply and demand. Recently, their coupling with renewable energy sources has been considered a strategic means of exploiting their high potential since it permits them to overcome their intrinsic uncertainty. Therefore, the storage systems integration with distributed generation can improve the performance of the networks and decrease the costs associated with energy production. However, a question remains regarding the overall environmental sustainability of the final energy production. Focusing on electrochemical accumulators, the problems mainly concern the use of heavy metals and/or impacting chemical components of storage at the center of environmental hazard debates. In this paper, an environmental assessment from a life-cycle perspective of the hybrid energy systems powered by fossil and renewable sources located on two non-interconnected minor islands is presented. Existing configurations are compared with new ones obtained with the addition of batteries for the exploitation of renewable energy. The results show that, for batteries, the assembly phase, including raw material extraction, transport, and assembly, accounts for about 40% of the total, while the remaining part is related to end-of-life processes. The reuse and recycling of the materials have a positive effect on overall impacts. The results also show that the overall impact is strongly related to the actual energy mix of the place where batteries are installed, even if it is usually lower than that of the solution without the batteries. The importance of a proper definition of the functional unit in the analysis is also emphasized in this work.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DeVanna2021,

title = {High-order conservative formulation of viscous terms for variable viscosity flows},

author = {Francesco De Vanna and Alberto Benato and Francesco Picano and Ernesto Benini},

doi = {10.1007/s00707-021-02937-2},

issn = {16196937},

year  = {2021},

date = {2021-01-01},

journal = {Acta Mechanica},

abstract = {The work presents a general strategy to design high-order conservative co-located finite-difference approximations of viscous/diffusion terms for flows featuring extreme variations of diffusive properties. The proposed scheme becomes equivalent to central finite-difference derivatives with corresponding order in the case of uniform flow properties, while in variable viscosity/diffusion conditions it grants a strong preservation and a proper telescoping of viscous/diffusion terms. Presented tests show that standard co-located discretisation of the viscous terms is not able to describe the flow when the viscosity field experiences substantial variations, while the proposed method always reproduces the correct behaviour. Thus, the process is recommended for such flows whose viscosity field highly varies, in both laminar and turbulent conditions, relying on a more robust approximation of diffuse terms in any situation. Hence, the proposed discretisation should be used in all these cases and, for example, in large eddy simulations of turbulent wall flows where the eddy viscosity abruptly changes in the near-wall region.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2020,

title = {Transient simulation on closure of wicket gates in a high-head Francis-type reversible turbine operating in pump mode},

author = {Wenjie Wang and Giorgio Pavesi and Ji Pei and Shouqi Yuan},

url = {https://doi.org/10.1016/j.renene.2019.07.052},

doi = {10.1016/j.renene.2019.07.052},

issn = {09601481},

year  = {2020},

date = {2020-01-01},

journal = {Renewable Energy},

volume = {145},

pages = {1817-1830},

abstract = {To solve the problem of grid instabilities, regulation in the Pumped Hydro Energy Storage (PHES) plants should quickly respond to the variation of electricity produced by unpredictable renewable energy. In this paper, a power reduction scenario applied to a pump turbine of a PHES is simulated considering the transient closure process of wicket gate. A novel dynamic mesh technique is applied to simulate the rotation of wicket gate vanes from best efficiency point to shutdown condition. Detached Eddy Simulation (DES) turbulence model is utilized to capture complex unsteady flow and the water weak compressibility effect is considered in the transient simulation. Flow rate, torque, power and pressure are analysed by the Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) methods. The results illustrate the delay between the performance parameters flow rate and power and the wicket gate opening angle. The closure of wicket gates affects the flow characteristics downstream the wicket gates greatly, causing intensive pressure fluctuations. The magnitude of pressure fluctuations downstream the wicket gate becomes the highest with the wicket gate closure of about 60%. Aside the blade passage frequency, a low frequency occurs, with the appearance of unsteady flow in pump turbine. Moreover, strong torque pulsations occur on the pin of the wicket vane when the percentage of closure is between 60% and 80%, with peaks much higher than that at the best efficiency point. The transient results can provide meaningful reference to the regulation law of wicket gate for safe operation of the pump turbine.},

keywords = {Closure of Wicket Gate, Dynamic Mesh, Energy storage, Francis-type Reversible Turbine, PHES, power reduction scenario, Pumped-hydro energy storage plant, transient flow},

pubstate = {published},

tppubtype = {article}

}

@article{Cavazzini2020b,

title = {Optimal assets management of a water distribution network for leakage minimization based on an innovative index},

author = {Giovanna Cavazzini and Giorgio Pavesi and Guido Ardizzon},

url = {https://doi.org/10.1016/j.scs.2019.101890},

doi = {10.1016/j.scs.2019.101890},

issn = {22106707},

year  = {2020},

date = {2020-01-01},

journal = {Sustainable Cities and Society},

volume = {54},

issue = {May},

pages = {101890},

publisher = {Elsevier},

abstract = {Leakage reduction in water distribution networks is an absolute priority and several pressure management strategies have been proposed in the literature to tackle this issue. However, the definition of an effective relationship between leakage and relevant and measurable parameters still represents a challenge. This paper presented a novel performance parameter, the Leakage Performance Index (LPI), to minimize leakages starting from pressure and flow rate measurements. This parameter creates a ranking among the different nodes in the network, by properly weighting the pressure of each node with the output flow from the node in order to focus the pressure management strategy on those nodes whose impact, in terms of leakage, is expected to be greater. To verify the effectiveness of the proposed LPI, a model of an existing water distribution district in Italy was developed in EPAnet and validated by comparison with experimental results. The valve settings of the model were then used as variables of time-dependent optimization procedures aimed at minimizing different objective functions. Different scenarios were considered by varying the minimum guaranteed pressure at the customer points. The LPI minimization strategy was efficient insofar as it indirectly minimized the leakages, achieving the same results of the leakage minimization strategy.},

keywords = {Energy performance indicators, Leakage, Optimization, Pressure management, Water distribution network},

pubstate = {published},

tppubtype = {article}

}

@article{Bonthuys2020b,

title = {Energy Recovery and Leakage-Reduction Optimization of Water Distribution Systems Using Hydro Turbines},

author = {Gideon Johannes Bonthuys and Marco Dijk and Giovanna Cavazzini},

url = {http://ascelibrary.org/doi/10.1061/%28ASCE%29WR.1943-5452.0001203},

doi = {10.1061/(ASCE)WR.1943-5452.0001203},

issn = {0733-9496},

year  = {2020},

date = {2020-01-01},

journal = {Journal of Water Resources Planning and Management},

volume = {146},

issue = {5},

pages = {04020026},

abstract = {Potential for energy recovery exists at any point within a water distribution system where the mechanical energy of excess water pressure can be converted into electrical energy. Energy conversion decreases the average operating pressure within a system, which in turn reduces water losses from leakages in the system due to the proportionality of leakage and pressure. This paper explores the incorporation of a genetic algorithm (GA) in a procedure to optimize the location and size of energy-recovery turbines (ERT) within a water distribution system based on maximizing recovered energy and reduced water losses evaluated on an economic basis and assigned a differentiated weighted importance. The developed procedure was tested on a well-known pressure management benchmark network as well as a water network from previous studies. Where previous studies on the benchmark network were only focused on pressure management, the current procedure produced results on pressure management with the added benefit of an analysis on both energy recovery and leakage reduction. The procedure provides municipal and water utility managers with a better-informed basis for pressure management and energy-recovery decision making.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bonthuys2020,

title = {The Optimization of Energy Recovery Device Sizes and Locations in Municipal Water Distribution Systems during Extended-Period Simulation},

author = {Gideon Johannes Bonthuys and Marco Dijk and Giovanna Cavazzini},

url = {https://www.mdpi.com/2073-4441/12/9/2447},

doi = {10.3390/w12092447},

issn = {2073-4441},

year  = {2020},

date = {2020-01-01},

journal = {Water},

volume = {12},

issue = {9},

pages = {2447},

abstract = {Excess pressure within water distribution systems not only increases the risk for water losses through leakages but provides the potential for harnessing excess energy through the installation of energy recovery devices, such as turbines or pump-as-turbines. The effect of pressure management on leakage reduction in a system has been well documented, and the potential for pressure management through energy recovery devices has seen a growth in popularity over the past decade. Over the past 2 years, the effect of energy recovery on leakage reduction has started to enter the conversation. With the theoretical potential known, researchers have started to focus on the location of energy recovery devices within water supply and distribution systems and the optimization thereof in terms of specific installation objectives. Due to the instrumental role that both the operating pressure and flow rate plays on both leakage and potential energy, daily variation and fluctuations of these parameters have great influence on the potential energy recovery and subsequent leakage reduction within a water distribution system. This paper presents an enhanced optimization procedure, which incorporates user-defined weighted importance of specific objectives and extended-period simulations into a genetic algorithm, to identify the optimum size and location of potential installations for energy recovery and leakage reduction. The proposed procedure proved to be effective in identifying more cost-effective and realistic solutions when compared to the procedure proposed in the literature.},

keywords = {energy recovery, Extended-period simulation, Genetic Algorithm, Leakage Reduction, Water distribution},

pubstate = {published},

tppubtype = {article}

}

@article{Macor2020b,

title = {A human health toxicity assessment of biogas engines regulated and unregulated emissions},

author = {Alarico Macor and Alberto Benato},

doi = {10.3390/app10207048},

issn = {20763417},

year  = {2020},

date = {2020-01-01},

journal = {Applied Sciences (Switzerland)},

volume = {10},

issue = {20},

abstract = {The aim of the work is to evaluate the damage to human health arising from emissions of in-operation internal combustion engines fed by biogas. The need of including also unregulated emissions like polycyclic aromatic hydrocarbons (PAHs), aldehydes and dioxins and furans is twofold: (i) to cover the lack in biogas engine emissions measurements and (ii) to complete the picture on biogas harmfulness to human health by identifying the substances with the highest impact. To this purpose, an experimental campaign is conducted on six biogas engines and one fed by natural gas all characterised by an electric power of 999 kWel. Collected data are used to perform an impact analysis on human health combining the Health Impact Assessment and the Risk Assessment. Measurements show that PAHs, aldehydes and diossin and furans are almost always below the detection limit, in both biogas and natural gas exhausts. The carcinogenic risk analysis of PAHs for the two fuels established their substantial equivalence. The analysis of equivalent toxicity of dioxins and furans reveals that biogas is, on average, 10 times more toxic than natural gas. Among regulated emissions, NOx in the biogas engines exhausts are three times higher than those of natural gas. They are the main contributors to human health damage, with approximately 90% of the total. SOx ranks second and accounts for about 6% of the total damage. Therefore, (i) the contribution to human health damage of unregulated emissions is limited compared to the damage from unregulated emissions, (ii) the damage per unit of electricity of biogas engines exhausts is about three times higher than that of natural gas and it is directly linked to NOx, (iii) obtaining a good estimation of the human health damage from both biogas and natural gas engines emissions is enough of a reason to consider NOx and SOx.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schiro2020,

title = {Modelling and analyzing the impact of hydrogen enriched natural gas on domestic gas boilers in a decarbonization perspective},

author = {Fabio Schiro and Anna Stoppato and Alberto Benato},

doi = {10.1016/j.crcon.2020.08.001},

issn = {25889133},

year  = {2020},

date = {2020-01-01},

journal = {Carbon Resources Conversion},

volume = {3},

abstract = {Decarbonization of energy economy is nowadays a topical theme, and several pathways are under discussion. Gaseous fuels have a fundamental role for this transition, and the production of low carbon-impact fuels is necessary to deal with this challenge. The generation of renewable hydrogen is a trusted solution since this energy vector can be promptly produced from electricity and injected into the existing natural gas infrastructure, granting storage capacity and easy transportation. This scenario will lead, in the near future, to hydrogen enrichment of natural gas, whose impact on the infrastructures is being actively studied. The effect on end-user devices such as domestic gas boilers, instead, is still little analyzed and tested, but is fundamental to be assessed. The aim of this research is to generate knowledge on the effect of hydrogen enrichment on the widely used premixed boilers: the investigations include pollutant emissions, efficiency, flashback and explosion hazard, control system and materials selection. A model for calculating several parameters related to combustion of hydrogen enriched natural gas is presented. Guidelines for the design of new components are provided, and an insight is given on the maximum hydrogen blending bearable by the current boilers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}